1. Field of the Invention
The present invention relates to an apparatus which uses the rotation in an axis across a square or round waveguide of a slab of dielectric material of predetermined dielectric coefficient and shape to provide a means of changing the differential phase shift between the orthogonal fields in the waveguide, as might be used to switch between linear and circular polarization in a high frequency microwave.
2. Description of the Prior Art
It is often necessary to provide a means of switching between linear and circular polarization or between polarization senses of a microwave signal as propagated by a conventional waveguide. A mechanism is required which adds a differential phase shift to one linear polarization compared to the orthogonal field.
FIG. 1 is a conventional rectangular waveguide. A waveguide is typically a metal fabrication having a top, bottom, two sides in a rectangular format which is operable to transmit high frequency microwave energy. Conventional waveguides can also be of the circular nature; and
FIG. 2 is an example of a circular waveguide. It too is operable to transmit high frequency microwave energy.
In order to provide a differential phase shift it is well known in the prior art to utilize a slab of dielectric material within the waveguide rotatable about the guide's longitudinal axis, round or circular, to provide a differential phase shift for the microwave signal.
Mechanical switching as described above has been done in any one of the following methods: movement of a dielectric slab laterally to the waveguide with a linear actuator and guide pins; rotation of the entire phasing section utilizing choke joints on each end of the phasing section; rotation of a longitudinal slab of dielectric about the waveguide axis using a circular waveguide as a bearing and with a gear teeth on the dielectric; or rotation of the dielectric in a circular waveguide by extending a dielectric rod through to a waveguide bend. These mechanical switching techniques as described are very complex techniques which require relatively easy access to the rotational mechanisms involved.